Direcitive traveling waves antenna



July 4, 1950 A, NlU-l-TA 2,513,736

DIRECTIVE TRAVELING WAVES ANTENNA Filed Feb. 25, 1948 EAST Mili TFTT mili W?? REC. REC.

Patented July 4, 1950 OFFICE DIRECTIVE TRAVELING WAVES ANTENNA I scanio Niutta, Rome, Italy Application February 25, 1948, Serial No. 10,903

In Italy June 24, 1946 section 1,1)ub1ie Law 690,` August 8, 1948 vPatent expires June24, 1066 8'Claims. (CI. 250-3351) This invention relates to antenna's and hasv for its principal. object the provision of a system whereby an antenna may 'receive simultaneously in either direction on a great circle. A further object of'the invention is to alter a um'directional receiving travelling-wave antenna so that it may receive not only in Vthe previous direction but lat an angle of 180` to the first direction, this result being obtained by adding a second receiverv at the other end of `the unidirectional antenna and arranging so that the input impedance of the two receivers and the characteristics yimpedance of the lines connecting the receivers to the antenna are made equal to the antenna output impedance.

A still further object of the invention is to arrange a single antenna to receive simultaneously in two opposite directions thereby permitting a saving in cost due to the less material and a saving in spacebecause a second antenna is thereby rendered unnecessary whether receiving on equal or on different .frequencies. A great advantage of such a system is that an emission from a great distance 'is sometimes received on the shorter path of a great circle passing through the sending and receiving stations but at other times the signal is best received by the longer route. By the present inventiona single antenna or a group of antennae is used. in which the impedance of the receiving equipment on either side of the antenna Vis equal to the antenna output impedance.

In the drawings: I v w Figure 1 shows a unidirectional antenna system. i

Figure 2 shows a system having two receivers and in which the messages can be received 'from directions at an angle of 180 to each other.

Figure 3 shows a similar system in which the antenna is of the so-called fish-bone double antennatype.

Figure 4 shows 'a system in which matching devices having a wide frequency response characteristic .are inserted in the line between veach end of the bi-directional antenna and the two receivers.

It is well known that when a receiving travelling-wave antenna is terminated on a circuit having the same impedance as the antenna,it 'becomes. unidirectional, receiving at theend 'opposite to the end at which the circuit is connected. Referring particularlyV to Figure 1, the conductors I, 2, 3, and 4 form a rhombic antenna in which the end 5 is connected by a transmission line 1 to the input circuit of the receiver 8.

Since, as is well known, the travelling-wave state is obtained only when the characteristic impedance ZO of the line 1 and the input impedance Zr of receiver 8 have their value equal to that of the antenna'impedance Ze which gives the relation Ze equals Zr equals Za, the opposite end 6 of antenna I, 2, 3, 4 is connected with a circuit 19 whose impedance is equal to the antenna impedance Za. When we have such a condition of equality between the impedance values of the antenna and the terminal circuit 9, theoretically there is no limitation to the constitution of vthe terminal circuit. However, from 'a practical standpoint in the case of a'receiving antenna the circuit is generally formed by a pure resistance of appropriate value whereas in the case of'a transmitting antenna it is usual to construct this circuit of a long dissipative line having characteristic impedance equal to that of the antenna. In order to understand more fully the'utility and `,aolvantages inherent in this invention, it may be well to note that thelunidirectivity of an antenna is a peouliarity of fundamental importance particyularly when receiving emissions from' great distances because in this way we obtain the'highest signal-to-noise ratioand we also eliminate interferences which come from a rearward direction, these including the very annoying interference due to various kin'ds of echo,

Furthermore, in receiving radio communications from great distances there are periods of the year and often certain hours of the .day in which it is easier to' receive electro-magnetic waves by the longer* pathv on the great circle through theV corresponding 'station than by the It `is because of such conditions as'thes'e that it has previously beenthought necessary to build a second antenna arranged at 'J to the first antenna in order to receive the signal with greatest assurance. In the case of diversity reception a second antenna group has been used. In other conditions which occur sometimes'in practice there are ltwo fand sometimes even more transmitting stations which are located substantially on the same great ci'rcle which passes through the receiving station andthe sending station. Under these conditions two'oppositely Aclirected antenna, or two antenna 'groups for diversity r'eception have been thought essential for proper reception.

In accordance with my invention, however, 'I am enabled by a verysimple system to use avsingle 'travelling-wave antenna of practical'ly any type and constitution for a satisfactory simultaneous reception of radio signals coming from either or both of the two opposite directions at the same or at different frequencies while preserving all of the advantages of the unidirectivity and aperiodicity and without altering in any way the original shape of the directivepattern of the antenna substantially irrespective of the type of antenna. The economy of installation is an important feature of my invention as it is readily seen that a considerable sa'ving offfnecessary material is obtained andin addition my system will cover a much smaller area of ground.

It is to be understood that the illustrations herewith are drawn in order to present the ,system clearly and they are not intended in any way to constitute a limitation on the basicpri-nciple of my invention. In Fig. 2 the same .l'hombic antenna is illustrated as in Fig. 1 and Aits impedance again is Za. The end of the `antenna is again connected With receiver 8- by-nieans of1 line 'I having as before the characteristic impedance Ze. The impedance input circuit of thereceiver 8 is Zr and we have again the relation Za equals ,Zelequals Z'r., In this figure, however, the other antennaend 6. ;instead vof being connected to the line 9 ;alone is now vconnected with a second receiver. .I ll preferably corresponding with lthe receiver In .this case the characteristic impedance `of line .9. isequal to the input impedance ofreceiver iii. and hothlof them are equal to' the .antenna impedance. v

`With the parts connected in this manner, the antenna is A correctly terminatedv at each Aof its :twdends in a, nianner to give receiver 8 a um'directional directive diagram as, for example, in an East direction. At 'the same time, the antenna ,has Similarly a unidirectional directive diagram for receiver .li-,0 indicated by the arrow bearing the legend West, merely meaning that the two directi've l diag-rams are. at 1.80 to each other. By such asimple and inexpe-nsive arrangement using only .one antenna, -it is possible to Acarry out two simul- 1taneous receptions vin the two opposite directions :f-:a

whilepreserving in each ycase the unidirectional characteristic, the gainl and the aperiodicty, .the latter being. ;a .peculiarity among others of th .antenna described.

While the rhombic antenna l,

and for any ,kind ofgroup vof them provided, of o course, that the impedanceequality conditions .arepreserved ;In some cases, the direct connection of the lines and the vantenna do not permit the equality condition which -is necessary between the values zof two-impedances Zjc and Za.y In such a case it meriely necessary :to employ suitable and well matching. devices such as H and 12l hav- ;ing- ;a wide .frequency response characteristic. Thepurpose of these-two ,devices is -to match re- ;spectillely the impedances of lines 'l and 3 to the impedance of the antenna in the points and 6 which are the two ends of the antenna. As previously pointed out, the impedances should be matched in the point of connection between each 2, 3 and 4 has 'i ;been shown in the first two figures, i-t is quite ob- 4 line and its respective receiver for the entire frequency band of the antenna.

What I claim is:

1. An antenna system including two receivers and a plurality o f conductors forming a travelingwave 'antenna each endwqfflwhich is connected to the input circuitof one-of the receive'rs; the input impedances' of the receive'rs beingr 'equal to each other and to the antenna output impedance whereby signals may be received um'directionally from v either or both .of two directions at an angle Of 180 to each other.

2. The system of claim 1 in which the conductors form a group of antennas.

'3. The system' of claim 1 in which a wide band matching device is positioned between the an- 'cenna andeach receiver.

'4. The system of claim 1 in which the antenna is rhQmbC.

5. The system of claim 1 in which the conduetors form .a double ,antenna of the fifih-bone type.

6. lA traveliing-wave receiyine antenna system 'in which a plurality of concluctors form an an- ,each have their value equal to the antenna ,im-

pedancev in which .casethe antenna becoines unidirectional, characterized by connecting aseconfd receiver by a line tosaidreceiving end of the antenna in whichthe impedance of the line and the input impedance of the ,second receiver are each .equal to .the ,antenna iinpedance whereby the unidi-rectional antenna becomes unidirectional in the previousdirection and also in adirection at 1 80 thereto whereby reception may be had through the tw o receivers from a receiving station on either the short arcof a great circle or on ;the longer ar-c 4Of thesamegreatcircle.

'L lThe Vsystem .of ,claim .6' in which the antenna is Ihmbic. ,and .a wide band mat ching de'- vice is inserted between `one .of the transmission lines to the receiverandthe antenna.

18. AV travelling-wave ,antenna system for the simultaneous unidirectiohal reception of two radio-waveshavng.edualor different frequencies, Vbut ;coming from'opposite directions, while main'- taining, independently for .each of said two ,directions, the same directivity pattern pertinent to the original unidirectional antenna, .comprising two receivers, a multi-,conductor vtraveling wave antenna and means'connecting the antenna vbetween the receivers, said connecting means vcomprising; transmission lines and means for matching `the imped-ance of ,the antenna to. the ltransmi-ssion linesandfv the impedance v.ofthe transmission lines` to the respective receivers l for the entire frequency range of the antenna. SCANIQ NIUTTA.

o REFE'RENCES ,ori'ED I The .followingrefer'ences :are`of recordV in the file of this patent:

UNITED vsit-firms`;PATENfrs Date Number Name 2,267,945 Peters Dec. 30,- l19,411 `2,290,314 f Carter ,July 21, 1:942

2303,"6110 .Cahter Dec. l', 1'942 

